In battery charging, a regulator 1A in a conventional battery charging apparatus 100A (see JP11-225446A, Patent Literature 1) rectifies an output current of an alternating-current generator “ACG” through a rectifying circuit 2 before charging a battery “B” (see FIG. 5), for example.
The conventional battery charging apparatus 100A includes the rectifying circuit 2, a battery detecting circuit 3 that detects whether or not the battery “B” is connected to the battery charging apparatus 100A, a full-charge detecting circuit 4 that detects a full charge of the battery “B”, and a driving circuit “DR” that controls driving and stopping of the rectifying circuit 2.
With the conventional battery charging apparatus 100A, in a state where a load “R” connected to the battery “B” is light or no load is connected to the battery “B”, the battery voltage can increase more than required if a screw securing the battery “B” loosens and a chattering occurs (a switch element “SW” is repeatedly turned on and off), for example.
For example, at an instant when the battery “B” is connected (the switch element “SW” is turned on), a current flows through a first path (1). Then, an average-value capacitor C1 in the full-charge detecting circuit 4 starts being charged, so that the start of operation of a transistor Tr2 in the full-charge detecting circuit 4 is delayed (see FIG. 6).
In the battery detecting circuit 3, the current flowing through the first path (1) triggers operation of a transistor Tr1, thereby causing a current to flow through a second path (2).
The current flowing through the second path (2) triggers operation of the first driving circuit “DR”, thereby causing a current to flow to the gates of thyristors to turn on the thyristors.
As a result, a current flows from the alternating-current generator “ACG” to a third path (3) through the rectifying circuit 2, and the battery “B” is charged.
On the other hand, when the battery “B” is released (the switch element “SW” is turned off), a current flows through the fourth path (4), and the average-value capacitor C1 in the full-charge detecting circuit 4 discharges (see FIG. 7).
In short, during a battery chattering, connection and release of the battery “B” successively occurs, the start of operation of the transistor Tr2 in the full-charge detecting circuit 4 is delayed each time the battery is connected, and thus, the battery “B” is excessively charged.
The above-described problem that the battery voltage increases more than required can arise in this way.
As described above, the regulator 1A according to prior art has a problem that the battery voltage increases beyond a full-charge voltage when a battery chattering occurs.